1. Technical Field
The embodiments described herein relate to a semiconductor integrated circuit, and in particular, to a digital temperature information generating apparatus for a semiconductor integrated circuit.
2. Related Art
In a semiconductor memory apparatus that writes data into a memory cell and outputs data written in the memory cell, an operation mode, called refresh, is necessarily performed to prevent data written in the memory cell from being lost. The refresh operation is divided into a self refresh operation, which is performed in the semiconductor memory apparatus itself, and an auto refresh operation, which is performed according to an external command.
The self refresh is cyclically performed in the semiconductor memory apparatus. Accordingly, the semiconductor memory apparatus needs a period signal for determining the timing of the self refresh operation. The period signal is also referred to as a self refresh signal, and is generated in the semiconductor memory apparatus.
To increase the efficiency of the self refresh operation, the period of the self refresh signal can be varied according to an ambient temperature.
An auto refresh operation also needs temperature information in order to vary the period of the auto refresh signal according to the ambient temperature. The JEDEC (Joint Electron Device Engineering Council) Mobile DRAM Standards define a refresh rate according to temperature information that is output through pads DQ8 to DQ10 of the DRAM.
At present, however, there is no hardware and software solution that allows the semiconductor integrated circuit to provide the temperature information.